Friends sled is a 08 xp 800 and has roughly 2800 miles on it. Took the carbs off 2 weeks ago and cleaned them all was good started and ran fine. Put it on the trailer and drove 450 miles to go sledding, got there and all was good, and rode all day. The next morning go to start it and it wouldn't start, pulled plugs and it was flooded bad, so with plugs out pulled over the motor, put plugs back in and it started and ran good all day. Next morning same thing, but this time with full choke and held throttle wide open a few pulls and it started and ran good all day. Now that were back home the check engine light is on and it is starting to run like crap, backfiring out the exhaust at idle. We take carbs back off to see if a float was hung up or something else and see nothing wrong in he carbs. Did a compression test and both cylinders are dead on at 124psi, not bad I thought. But still dumping fuel in the cylinders so badly that when it starts fuel comes out the pipe. Any ideas o what might have happened?

Rarely do you need to replace the needle/seats. What fails is the O-ring for the seat assembly. When you remove the float assembly you will see the o-ring. It seals the seat to the carb. When this fails fuel sneaks by.

The o-ring cannot be bought separately from Doo, but can be from Cat. Call BJ @ SHR for the part #.